title: Label-free in vitro toxicity and uptake assessment of citrate stabilised gold nanoparticles in three cell lines.
abstract: BACKGROUND
  Reliable in vitro toxicity testing is needed prior to the commencement of in vivo testing necessary for hazard identification and risk assessment of nanoparticles. In this study, the cytotoxicity and uptake of 14 nm and 20 nm citrate stabilised gold nanoparticles (AuNPs) in the bronchial epithelial cell line BEAS-2B, the Chinese hamster ovary cell line CHO, and the human embryonic kidney cell line HEK 293 were investigated.
  
  
  METHODS
  Cytotoxicity of the AuNPs was assessed via traditional XTT-, LDH-, and ATP-based assays, followed by cell impedance studies. Dark-field imaging and hyperspectral imaging were used to confirm the uptake of AuNPs into the cells.
  
  
  RESULTS
  Interference of the AuNPs with the XTT- and ATP-based assays was overcome through the use of cell impedance technology. AuNPs were shown to be relatively non-toxic using this methodology; nevertheless CHO cells were the most sensitive cell type with 20 nm AuNPs having the highest toxicity. Uptake of both 14 nm and 20 nm AuNPs was observed in all cell lines in a time- and cell type-dependent manner.
  
  
  CONCLUSIONS
  Using the cell impedance and dark-field hyperspectral imaging technologies, it was possible to study the toxicity of AuNPs in different cell lines and show that these cells could internalize AuNPs with their subsequent intracellular aggregation. It was also possible to show that this toxicity would not correlate with the level of uptake but it would correlate with cell-type and the size of the AuNPs. Therefore, these two label-free methodologies used in this study are suitable for in vitro studies on the effects of AuNPs, and could present themselves as appropriate and valuable methodologies for future nanoparticle toxicity and uptake studies.
authors.affiliation: Toxicology Section, National Institute for Occupational Health (NIOH), P O Box 4788, Johannesburg 2000, South Africa. mary.gulumian@nioh.nhls.ac.za.
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Vetten
authors.forename: Nonhlanhla
authors.initials: N
authors.lastname: Tlotleng
authors.forename: Delia
authors.initials: D
authors.lastname: Tanner Rascher
authors.forename: Amanda
authors.initials: A
authors.lastname: Skepu
authors.forename: Frankline K
authors.initials: FK
authors.lastname: Keter
authors.forename: Kailen
authors.initials: K
authors.lastname: Boodhia
authors.forename: Leigh-Anne
authors.initials: LA
authors.lastname: Koekemoer
authors.forename: Charlene
authors.initials: C
authors.lastname: Andraos
authors.forename: Robert
authors.initials: R
authors.lastname: Tshikhudo
authors.forename: Mary
authors.initials: M
authors.lastname: Gulumian
mesh_terms: D000818:Animals; D016466:CHO Cells; D018929:Cell Culture Techniques; D002470:Cell Survival / Q000187:drug effects; D019343:Citric Acid / Q000737:chemistry*; D006224:Cricetinae; D003412:Cricetulus; D017097:Electric Impedance; D004847:Epithelial Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D006046:Gold / Q000737:chemistry / Q000633:toxicity*; D057809:HEK293 Cells; D006801:Humans; D053768:Metal Nanoparticles / Q000737:chemistry / Q000633:toxicity*; D046529:Microscopy, Electron, Transmission; D010316:Particle Size; D025341:Principal Component Analysis; D013499:Surface Properties; D018675:Toxicity Tests / Q000379:methods*
chemical_list: D019343:Citric Acid; D006046:Gold